Why they pair well
A heat pump is most efficient when it delivers heat at a low water temperature. The Energy Saving Trust says that heat pumps send water to radiators at lower temperatures than an equivalent fossil-fuel system, often between 35 and 45°C. Underfloor heating suits that pattern: the whole floor acts as one large radiator, so it can warm a room without needing hot water. The Trust states that underfloor heating usually works well for heat pumps.
The link to efficiency is the flow temperature. In the Energy Systems Catapult trial the median COP was 3.5 at a 35°C flow and 2.38 at 55°C; the lower the water temperature, the more heat per unit of electricity. The mean flow temperature across the trial’s air source units was 39.7°C. The efficiency guide sets out how that translates into a seasonal figure.
Retrofitting underfloor heating
The Trust says you may be able to fit underfloor heating instead of radiators. It is realistic about the disruption: fitting underfloor heating means taking up floor coverings and floorboards, and it lists underfloor heating among the factors that can make an installation take longer than the typical three days. The full job also depends on your floor construction, the room heights, door thresholds and floor finishes, none of which this site can assess. A survey is the point at which an installer should tell you what is possible in each room.
For most homes replacing a boiler, the practical question is not underfloor heating or nothing; it is which radiators to upgrade. The Trust notes that single-panel radiators can be swapped for double or triple panels to increase surface area without taking more wall space. The sizing and radiators guide covers how that decision is made from the heat-loss calculation.
Underfloor heating vs radiators
| Question | Underfloor heating | Radiators on a heat pump |
|---|---|---|
| Water temperature needed | Low; large emitting area | Low, but bigger or more radiators may be needed (the Trust says 35 to 45°C is typical) |
| Disruption in an existing house | Floors lifted; adds time | Radiators swapped; pipework changes where needed |
| Wall space | None used | Radiators need wall space; double or triple panels add output without extra width |
| Best suited to | New builds, extensions and renovations with floors up | Most boiler replacements |
| Quote line to look for | Floor works, manifolds, controls priced per room | Number and size of radiators changed |
Underfloor heating tends to be slow to respond, which suits the heat pump advice to keep the system running at a steady level. If your house is a new self-build, which can qualify for the grant while a developer-built new home cannot, underfloor heating is easiest to plan into the floor build-up; see the eligibility page for the property rules.
What it does to efficiency
Lower flow temperatures raise the seasonal figure, and an installer who designs for underfloor heating can usually set a lower heating curve. But the emitter type is only one input: in the trial 91.9% of properties measured below their designed seasonal figure, so design and commissioning matter as well. The controls guide explains the settings involved.
Is underfloor heating worth it with a heat pump?
On efficiency, yes, because underfloor heating runs at a lower water temperature, and a heat pump is most efficient at low temperatures. The Electrification of Heat trial measured the median system at 3.5 units of heat per unit of electricity with a 35°C flow, against 2.38 at 55°C. On cost, it depends: retrofitting underfloor heating means lifting floors, which is a large job in an occupied house, and the grant is a fixed amount that does not rise for it, so the extra work adds to the balance you pay. Larger radiators can often get close to the same flow temperature for less disruption.
Ask for the options priced separately. The grant comes off the whole installation quote and stays the same whichever emitters you choose; see air source heat pump cost for the official median and what a full quote includes.
What to ask installers to price
- A room-by-room heat-loss calculation, with the flow temperature each option assumes.
- Radiator-only, underfloor-only and mixed options, each priced as separate lines.
- Who lifts and relays floor coverings, and who is responsible for them.
- How long the job will take and how you keep warm while the heating is off.
- That the grant (currently £7,500 for air source and ground source in England and Wales) is shown as a deduction, separate from any floor work.
On cost, remember the official 2026 Q3 median for an installed air source heat pump was £12,826 including the grant (DESNZ), and this guide has no verified price for retrofitting underfloor heating, so ask for it as a separate line; the installation cost guide breaks down the lines. Use the quotes checklist to compare options.